Hi guys - sorry I haven't been around here. I've been too focused on that resolver driver thing. Recently I've been looking into the temp sensor on the MGR. Here's what I've found:
According to the FSM, the temp sensor is simply a variable resistor. Pin 1 of the connector is one side of the thermistor, and Pin 3 is the other side. It should be isolated from the case. On the controller side, Pin 3 is connected to the controller ground and Pin 1 is connected to 5V and voltage sensing circuitry which they don't detail. The thermistor works in a range of -50C to 204C. When debugging their system, if the temp sensor reports -50C, there is an open circuit and if it reports 205C, there is a short to ground.
I measured the resistance across pins 1 and 3 and found the resistance to be 57.6kOhms at a temperature of 24.1C. I measured it when the room was hotter and got a reading of 48kOhms.
From this, I'm going to assume it's a 50kOhm NTC thermistor. I'll add a little driver circuit consisting of a 50kOhm 1% resistor connected to the 5V board power supply. The circuit's output will go to the "Index" AtoD converter pin of the DSPic.
If anyone has any suggestions regarding this, please let me know before it becomes a permanent feature of the resolver driver adapter.
I did post some links from Tamagawa about the resolver and the special decoder they made for it. It's all pretty interesting with excellent information about setting up a resolver system. The Prius apparently uses two of these, along with two of the decoders. Maybe I posted them in the controller thread. If you can't find them, let me know.
Personally, I don't see any advantage to rewinding the motor. It could help if the voltage could be lowered to around 100V - that would be in standard EV territory. However, if it's dropped by a factor of two - that's still around 300V
That's the voltage my solar system runs at, and believe me - I don't feel safe in messing with stuff. In other words - be REALLY careful, whether it's 300V or 650V.
Regarding cooling - that's one of the main reasons I started this thread.
Getting the oil in and out of the MGR will be easy. There are several ports that should work great for that task. I don't think we'll need to drill & tap any additional holes.
My main hangup is how best to circulate the oil. If the MGR is mounted similar to the OE setup, with the motor forward, this should be NBD. In this case, the oil circulation is merely additional cooling. If the pump fails the temperature will increase, but everything will still be lubricated.
If the MGR is mounted backwards (like I have to do for lack of space in my back drive) then the circulating pump becomes critical. It now also supplies lubrication for all the gears and bearings and critical cooling for the motor. If the pump fails in this case, there will be a rapid increase in temperature and potentail damage to the bearings and gears.
Given the critical nature of the pump in the second scenario, I've spent a bit of time looking for good options. Here are a few things I've found:
1) electric oil pumps for turbochargers. Good ones are made with the knowlege that if the pump fails, the turbo will quickly fail. Problem: they cost as much as a used MGR.
2) Oil pumps for motorcycles. I've found good options from Harley Davidson, BMW, and some Kawasaki racing bikes.
3) The Prius transmission's oil pump
The pumps for the Prius and the motorcycles are all gerotor type pumps. In general, gerotor pumps can be described as one gear inside an internal gear with 1 tooth difference between the two.
We may be able to drive a pump directly from the motor. There's a vibration damper which seems to me to be merely a chunk of steel bolted to the outside of the motor side of the MGR case. It is concentric with the motor bearing, and it may be possible to drive a pump by removing the balancer and replacing it with an oil pump.
Thoughts?